Lignin is a major component of wood (seen as brown material), also present in non-wood plants. This heterogeneous polyphenolic compound provides rigidity to the wood structure and protects cellulose fibers from damage. Naturally, lignin creates a major hurdle to recovering cellulose for paper making or other applications. Mechanical pulping of wood is extremely energy intensive process; for example, a typical newsprint pulp may need 2160 kWh of refiner energy per ton of feedstock to refine wood chips into pulp. Reducing this energy requirement is a very acute need of the industry.
As one of the solutions, enzymes capable of oxidizing lignin were proposed to be used for pretreatment of wood chips (material for pulping) in order to decrease the energy required for grinding. This idea was perceived from natural observation that fungi, especially white-rot fungi are able to decay wood material by secreting lignolytic enzymes such as peroxidases and laccases.
This idea was first implemented as so-called bio-pulping, when fungal species were actually cultivated on wood chips before pulping. This resulted in substantial energy saving, but cultivation time comprised several weeks, which was not acceptable in industrial context.
Subsequently, it was proposed to use isolated enzyme preparations for wood pretreatment, rather than live species, which should in principle produce similar effect. This resulted in a limited number of publications wherein isolated fungal laccases were employed for wood chips pretreatment.
There remains a need in the art for enzymes with an improved performance, in terms of cost-effective lignin oxidation, energy saving in the process, speed of action, safety, stability and potential for development.